Conventionally, floppy disk drive (hereinafter called FDD) units, CD-ROM drives, etc. are used as external recording devices for recording data for personal computers (hereinafter called PCs).
These external recording devices are connected to PCs via an interface called IDE or SCSI. Such external recording devices and other devices connected externally to the PC, as well as hardware internal to the PC, are controlled for operation by software called an operating system (hereinafter called OS) the representative examples of which include Windows 98, MacOS, and UNIX.
The OS employs a concept called file system for the overall management of file name, file recording date, file length, file recording location and other information relating to data (file) recorded or to be recorded on a medium of an external recording device such as an FDD or CD-ROM drive.
In the OS called Windows 98, for example, the file system employed for FDD units is called FAT (File Allocation Table) and that for CD-ROM drives is called CDFS (CD File System).
Software responsible for the file system is the file system driver (hereinafter called FSD) which is included as a part of the OS. Using the FSD, it becomes possible to perform manipulations such as recording data (file) on a medium of an external recording device and reproducing data (file) recorded thereon.
In recent years, digital interfaces based on new standards such as the IEEE 1394 standard have been introduced for PCs, enabling devices, such as a DV for recording or reproducing digital multimedia information containing video and audio data on a magnetic tape, to be connected to PCs.
Thus, when connecting an external device to a PC using an IEEE 1394 interface, the OS of Windows 98 requires the use of a driver conforming to the IEEE 1394 standard, that is, a WDM (Windows Driver Model) driver designed to WDM architecture, a new architecture different from the existing architecture.
Next, data transfers between a PC and an FDD unit and DV will be described with reference to FIG. 4 when the OS of Windows 98 is used. FIG. 4 is a diagram for explaining a connection verifiable information processing apparatus of a prior art when Windows 98 is used. The connection verifiable information processing apparatus here means the PC described above.
In FIG. 4, reference numeral 50 is the connection verifiable information processing apparatus of the prior art, 3 is a display application for displaying connection state, 5 is a system service, 6 is an I/O manager subset, 7 is a WDM driver, 8 is a WDM compliant device, 11 is an IFS manager, 12 is a first FSD, 14 is an I/O subsystem, 15 is a WDM non-compliant device driver, 16 is a WDM non-compliant device, 40 is a system virtual machine, and 20 is a display screen (monitor).
As shown in FIG. 4, the connection verifiable information processing apparatus 50 is connected to the WDM non-compliant device 16 via the WDM non-compliant device driver 15, and to the WDM compliant device 8 via the WDM driver 7.
For convenience of explanation, the following description assumes that the WDM non-compliant device 16 is an FDD unit, that is, a device for recording moving image data of digital video and audio on a floppy disk (hereinafter called FD) or reproducing the moving image data recorded thereon.
On the other hand, the WDM compliant device 8 is assumed to be a DV, that is, a device for recording moving image data of digital video and audio on a magnetic tape or reproducing the moving image data recorded thereon.
Here, when transferring contents such as document data or video data from the connection verifiable information processing apparatus 50 to the WDM non-compliant device 16 (FDD unit), the contents are transferred to the WDM non-compliant device 16 (FDD unit) via the system virtual machine 40, IFS manager 11, first FSD 12, I/O subsystem 14, and WDM non-compliant device driver 15.
Conversely, when transferring contents from the WDM non-compliant device 16 (FDD unit) to the connection verifiable information processing apparatus 50, the contents are transferred along the same route but in the opposite direction. The route along which contents are transferred between the connection verifiable information processing apparatus 50 and the WDM non-compliant device 16 (FDD unit) is referred to as the route 1.
In FIG. 4, the WDM non-compliant device driver 15 provides an interface between the connection verifiable information processing apparatus 50 and the WDM non-compliant device 16 (FDD unit), and the I/O subsystem 14 controls the file system of FAT supported by Windows 98.
The IFS manager 11 is the overall management part in order to allow the data used in the file system format to be used by application software such as a playback application. The playback application is not shown in FIG. 4. The system service 5 provides the role of an interface between the IFS manager 11 and an application such as a playback application.
On the other hand, when transferring contents such as video data from the connection verifiable information processing apparatus 50 to the WDM compliant device 8 (DV), the contents are transferred to the WDM compliant device 8 via the system virtual machine 40, I/O manager subset 6, and WDM driver 7.
Conversely, when transferring contents from the WDM compliant device 8 (DV) to the connection verifiable information processing apparatus 50, the contents are transferred along the same route but in the opposite direction. The route along which contents are transferred between the connection verifiable information processing apparatus 50 and the WDM compliant device 8 (DV) is referred to as the route 2.
Transfer of contents between the connection verifiable information processing apparatus 50 and the WDM compliant device 8 (DV) is implemented using isochronous data transfer as defined in IEEE 1394.
In that case, however, since the contents are transferred along the above-described route 2, that is, since no file system is available for the WDM compliant device 8 (DV), the data (file) recorded on a magnetic tape in the WDM compliant device 8 (DV) cannot be handled in a file format, like the data (file) recorded on an FD in the WDM non-compliant device 16 (FDD unit) is handled in a file format.
If a file system were devised for the WDM compliant device 8 (DV), and an FSD for the DV file system were used, it would not be possible to directly use the route containing the FSD, since the DV is a WDM non-compliant device as described above.
Furthermore, the route 1 is used for the transfer of contents between the connection verifiable information processing apparatus 50 and the WDM non-compliant device 16 (FDD unit) and the route 2 for the transfer of contents between the connection verifiable information processing apparatus 50 and the WDM compliant device 8 (DV), and it is not possible to transfer data laterally between the route 1 and the route 2, for example, to transfer data by connecting the WDM driver 7 with the first FSD 12.
The WDM driver 7 provides an interface between the connection verifiable information processing apparatus 50 and the WDM compliant device 8 (DV), and the I/O manager subset 6 has the function of controlling the overall operation of the WDM driver 7. The system service 5 provides not only an interface between the IFS manager 11 and an application such as a playback application, but also an interface between the I/O manager subset 6 and an application such as a playback application.
Data transfers between the connection verifiable information processing apparatus 50 and the WDM non-compliant device 16 (FDD unit) and WDM compliant device 8 (DV) have been described above with reference to FIG. 4; next, the connections between the connection verifiable information processing apparatus 50 and the WDM non-compliant device 16 (FDD unit) and WDM compliant device 8 (DV) will be described using the same FIG. 4.
As described above, when the WDM non-compliant device 16 (FDD unit) or the WDM compliant device 8 (DV) is connected to the connection verifiable information processing apparatus 50, data can be transferred between the connection verifiable information processing apparatus 50 and the WDM non-compliant device 16 (FDD unit) or the WDM compliant device 8 (DV) through the route 1 or the route 2, but if they are not connected, data cannot be transferred.
Accordingly, the connection verifiable information processing apparatus 50 examines whether or not it connects to the WDM non-compliant device 16 (FDD unit) and WDM compliant device 8 (DV).
First, a description will be given of how the connection verifiable information processing apparatus 50 examines whether or not it connects to the WDM non-compliant device 16 (FDD unit).
To examine whether or not the WDM non-compliant device 16 (FDD unit) is connected to the connection verifiable information processing apparatus 50, the system service 5 in the connection verifiable information processing apparatus 50 issues a first transmit request to the IFS manager 11 to request an output of information concerning the connection. The first transmit request is transferred from the IFS manager 11 to the WDM non-compliant device driver 15 via the first FSD 12 and I/O subsystem 14, and is output from the WDM non-compliant device driver 15.
The first transmit request output from the WDM non-compliant device driver 15 is input to the WDM non-compliant device 16 (FDD unit) if the WDM non-compliant device 16 (FDD unit) is connected to the connection verifiable information processing apparatus 50; responding to the first transmit request, the WDM non-compliant device 16 (FDD unit) outputs response information containing information concerning its own device type, i.e., FDD unit. The response information is returned to the system service 5 via the route 1.
In this way, when the response information is returned to the system service 5, it is determined that the WDM non-compliant device 16 (FDD unit) is connected to the connection verifiable information processing apparatus 50.
On the other hand, if the WDM non-compliant device 16 (FDD unit) is not connected to the connection verifiable information processing apparatus 50, the first transmit request output from the WDM non-compliant device driver 15 is not input to the WDM non-compliant device 16 (FDD unit) and, therefore, no response information is output; as a result, the connection verifiable information processing apparatus 50 does not receive any response information.
That is, no response information is returned to the system service 5. In this way, when no response information is returned to the connection verifiable information processing apparatus 50, it is determined that the WDM non-compliant device 16 (FDD unit) is not connected to the connection verifiable information processing apparatus 50.
The information concerning the connection of the WDM non-compliant device 16 (FDD unit) to the connection verifiable information processing apparatus 50 is transferred from the system service 5 to the display application 3 for display on the display screen 20 when there is a user instruction. By viewing the connection information displayed on the display screen 20, the user can verify whether or not the WDM non-compliant device 16 (FDD unit) is connected to the connection verifiable information processing apparatus 50.
Application software called “Microsoft Explorer” has been known in the prior art as a specific example of the display application 3.
Next, a description will be given of how the connection verifiable information processing apparatus 50 examines whether or not it connects to the WDM compliant device 8 (DV).
To examine whether or not the WDM compliant device 8 (DV) is connected to the connection verifiable information processing apparatus 50, the I/O manager subset 6 in the connection verifiable information processing apparatus 50 issues a second transmit request to the WDM driver 7 to request an output of information concerning the connection. The second transmit request is then output from the WDM driver 7. The second transmit request output from the WDM driver 7 is input to the WDM compliant device 8 (DV) if the WDM compliant device 8 (DV) is connected to the connection verifiable information processing apparatus 50. Responding to the thus input second transmit request, the WDM compliant device 8 (DV) outputs response information containing information concerning its own device type, i.e., DV. The response information is input to the WDM driver 7 and transferred to the I/O manager subset 6.
In this way, when the response information is returned to the I/O manager subset 6, it is determined that the WDM compliant device 8 (DV) is connected to the connection verifiable information processing apparatus 50.
On the other hand, if the WDM compliant device 8 (DV) is not connected to the connection verifiable information processing apparatus 50, the second transmit request output from the WDM driver 7 is not input to the WDM compliant device 8 (DV) and, therefore, no response information is output; as a result, no response information is returned to the I/O manager subset 6.
Further, when the WDM compliant device 8 (DV) is not connected to the connection verifiable information processing apparatus 50, the whole or part of the WDM driver 7 may not exist. In that case, the I/O manager subset 6 cannot issue the second transmit request, nor does it receive any response information.
In this way, when no response information is returned to the I/O manager subset 6, it is determined that the WDM compliant device 8 (DV) is not connected to the connection verifiable information processing apparatus 50.
As earlier described, the information concerning the connection of the WDM non-compliant device 16 (FDD unit) to the connection verifiable information processing apparatus 50 is displayed on the display screen 20 by the display application 3.
However, the information concerning the connection of the WDM compliant device 8 (DV) to the connection verifiable information processing apparatus 50 is not displayed on the display screen 20 by the display application 3.
This is because the display application 3 is a means for displaying the “connection information” processed by the system service 5 and the “information concerning the connection of the WDM compliant device 8 (DV) to the connection verifiable information processing apparatus 50” is not processed by the system service 5.
More specifically, the format of the “connection information” output from the WDM driver 7 is different from the format of the “connection information” that the system service 5 can process, and the I/O manager subset 6 does not have the function of converting the format of the “connection information” output from the WDM driver 7 into the format of the “connection information” that the system service 5 can process.
Accordingly, even if the WDM driver 7 and the I/O manager subset 6 have the “information concerning the connection of the WDM compliant device 8 (DV) to the connection verifiable information processing apparatus 50”, the system service 5 cannot process the information.
As a result, even in cases where devices which can be connected or disconnected from a PC (such as a DV) can be connected to or disconnected (detached) from a PC while the PC is operating, by using an interface conforming to the IEEE 1394 standard (connecting/disconnecting of a device while the PC is operating is hereinafter called Hot Plugging), the information concerning the connection or disconnection is not displayed on the display screen 20 by the display application 3 although the WDM driver 7 can have such information. Therefore, using “Microsoft Explorer”, a list of information concerning the connections of the PC and external connection devices cannot be displayed on the monitor to present hot plugging information of each device: presenting hot plugging information means that if a device is connected, the folder for that device is displayed on the monitor and, if the device is disconnected, the folder for that device is not displayed.
Next, consider the case where an existing storage device (a device corresponding to the WDM non-compliant device 16 in FIG. 4) is connected to the PC (the connection verifiable information processing apparatus 50) and the connection state of the existing storage device thus connected is displayed on the monitor by using “Microsoft Explorer” as the display application 3.
For a device icon, if the device is an FDD unit, the same FDD folder is displayed irrespective of the manufacturer of the FDD, and if the device is a CD-ROM drive, the same CD-ROM drive folder is displayed irrespective of the manufacturer of the CD-ROM drive.
Accordingly, by only viewing the monitor, the user cannot identify the manufacturer of the connected device and, if the device is the same and is from the same manufacturer, there is no knowing when the device was manufactured, that is, whether the device is a new model or an old model.
This is because the WDM non-compliant device 16 in FIG. 4 does not carry manufacturer or manufacturing date information in the response information and information concerning the manufacturer, manufacturing date, etc. is therefore not supplied to the system service 5.
“Microsoft Explorer” is an application that, if information concerning the manufacturer, manufacturing date, etc. is input and processed by the system service 5, can present a display by distinguishing not only the type of the device but also the manufacturer, manufacturing date, etc. based on the information processed by the system service 5.
Accordingly, if information concerning the manufacturer, manufacturing date, etc. is input together with the information identifying the type of the device for processing by the system service 5, then the type of the device, the manufacturer, and the date of manufacturing will be displayed on the display screen 20.
Consider here a DV as a specific example of the WDM compliant device 8. In this case, this DV outputs information concerning the type of the device, the manufacturer, the date of manufacturing, etc. upon receiving the second transmit request from the WDM driver 7; that is, the information concerning the type of the device, the manufacturer, the date of manufacturing, etc. output from the WDM compliant device 8 can be input to the WDM driver 7. This means that if this information is input and processed by the system service 5, then the information identifying not only the type of the device but also the manufacturer, manufacturing date, etc. can be displayed on the display screen 20 by “Microsoft Explorer” as the display application 3.
To summarize the above, the prior art has had the problem that the information processing means which processes response information to the first transmit request, said response information being described following the first format, that the first transmit request means which issues the first transmit request issues to request an output of connection information cannot process response information to the second transmit request, said response information being described following the second format, that the second transmit request means which issues the second transmit request issues to request an output of connection information different from that requested by the first transmit request means.
Here, the first transmit request means and the information processing means together correspond to the system service 5 in FIG. 4. The second transmit request means corresponds to the I/O manager subset 6 in FIG. 4.
On the other hand, a DV (Digital Video Cassette) using a magnetic tape has been around as a medium for storing multimedia information containing video and audio. Currently, studies are under way to connect the DV to a PC (personal computer) and use it as a computer storage medium like the existing media such as hard disks and floppy disks.
A previously proposed DV for the current TV signal (hereinafter called the SD-DV) will be shown below as a prior art example.
In FIG. 14, reference numeral 201B is a recording and playback apparatus. Reference numeral 203 is a cassette for recording data formatted, error correction coded, modulated, etc. by a recording and playback processing circuit 206B. Reference numeral 206B is the recording and playback processing circuit that applies processing such as formatting, error correction coding, and modulation on the data received via an interface 205. Reference numeral 205 is the interface which transfers data, received from an external device, to a controller 111 as well as to the recording and playback processing circuit 206B.
The operation of the recording and playback apparatus having the above configuration will be described below.
Data transmitted from the external device and received by the recording and playback apparatus 201B via the interface 205 is formatted (for data reordering, appending of auxiliary information), error correction coded, modulated, etc. by the recording and playback processing circuit 206, and then recorded on the cassette 203. The recording track format is shown in FIG. 6.
Each track is divided into ITI, Audio, Video, and Subcode sectors. The Audio sector comprises nine audio data recording packets (sync blocks) and five parity recording packets (sync blocks) for recording parity data resulting from the error correction coding of data (in this example, error correction outer code).
The Video sector comprises 135 video data recording packets (sync blocks), 11 parity recording packets (sync blocks), and a total of three VAUX recording packets (sync blocks) for recording information indicating video format, etc.
FIGS. 7(1) and 7(2) show video data recording packet formats.
The recording packet shown in FIG. 7(1) is a 25-Mbps mode DVC packet which contains DCT (discrete cosine transform) coded data in six DCT blocks (Y1 to Y4, CR, and CB). Within each DCT block, the DC component (indicated by DC in the figure) of the DCT coded data is placed in a fixed position shown in FIG. 7(1), which is followed by AC components (indicated by AC in the figure), EOB (end of block) code, etc. The EOB code is a code indicating that the DCT block contains no further data after the position where the code is placed.
On the other hand, FIG. 7(2) shows a low-rate 12.5-Mbps mode DVC packet which comprises eight DCT blocks; in this case also, within each DCT block the DC component is placed in a fixed position, as in the above case. Two-byte sync information, three-byte ID information, and eight-byte error correction inner code are appended to each recording packet.
The existing digital VTR described above is only allowed to record video and audio signals of a designated format, and if a tape on which PC file data is recorded in its original form is played back, there arises the problem that the tape is erroneously recognized or trouble occurs such as the generation of noise (the noise may destroy audio output equipment) or abnormal video output.
Furthermore, it does not provide a function such as file-by-file access which is possible, for example, with a hard disk connected to a PC, and it is therefore difficult to readily know the contents or quickly access the location of the desired contents. Japanese Patent Application No. 09-067653 is devised to solve this problem.
While the prior art allows the recording of ordinary PC data as well as DV data, as described above, the prior art has had the problem that it cannot provide the high error correction capability required for PC data when PC data usually demands a higher error correction quality than DV data does.
More specifically, in the case of video data such as DV data, if an error occurs, only a frame that is displayed for 1/30 second or a portion of the frame is disrupted and, since the resulting degradation in picture quality is virtually imperceptible to the user (viewer), it does not present much of a problem. On the other hand, in the case of PC data, if a single byte of data is in error, the file itself may not be able to be opened, and in the worst case, there may be danger that it damages the PC itself.
The above prior art refers also to a method of recording the same data a plurality of times to enhance the error correction capability, but this method is extremely inefficient from the viewpoint of recording capacity, and there has been a need for a method that can increase the error correction capability efficiently.
On the other hand, with advances in LSI technology, development of networks for transmitting video and audio information in digital form has been proceeding. Since video and audio signals must be reproduced in real time, there arises a need for a network capable of realtime transmission.
A network called IEEE 1394 is proposed as a network suited for such realtime transmission. IEEE 1394 is a serial high-speed bus system and is capable of realtime transmission since it allows synchronous transmission of data.
IEEE 1394 is mounted as an external interface in many digital video/audio apparatuses including home digital VCRs (hereinafter referred to as DVs). In a DV, for example, by using IEEE 1394, it becomes possible to control the operation of the DV from an external device or to transmit data to the DV from an external device and record and/or play back the data on the DV.
Furthermore, in personal computers (hereinafter referred to as PCs), IEEE 1394 is rapidly spreading in the world of PCs because IEEE 1394 is officially supported by Microsoft Windows 98, the standard OS.
In view of this, work has been proceeding for the fusion of PCs and digital video/audio apparatuses such as DVs.
A method of controlling the operation of a DV from a PC and a method of transmitting data from a PC to a DV and playing back the data on the DV will be described with reference to FIGS. 23 and 24.
FIG. 23 shows an example of a PC and DVs connected to an IEEE 1394 bus. In FIG. 23, reference numeral 1103 is the IEEE 1394 bus; 1104, 1504a, and 1504b are IEEE 1394 interfaces; 1108, 1108a, and 1108b are commands; 1109 is a device number; 1301 is the PC; 1502a and 1502b are the DVs; 1503a and 1503b are recording and playback circuits; 1505 is data; 1506a is a monitor; and 1507a is a reproduced video image.
FIG. 24 shows an example of node ID and device number assigned to the DV 1502a and DV 1502b. 
First, a description will be given of a method of assigning the device number (1109) necessary for the PC 1301 to access the respective DVs.
On the IEEE 1394 bus 1103, a unique value called a node ID is assigned to each DV. Assume, for example, that 1 is assigned to the DV 1502a and 2 to the DV 1502b. When the number of devices connected to the IEEE 1394 bus 1103 is changed, or when a certain device explicitly causes a bus reset, the node IDs are reassigned, but in this case, each device is not always assigned the same node ID value as previously assigned.
To access the respective DVs, the PC 1301 assigns the device number (1109) to each DV when power is turned on to the PC 1301 or when the PC 1301 is newly connected to the IEEE 1394 bus 1103. In one method of assignment, if provisions are made to assign numbers 0, 1, 2, . . . in sequence to the DVs, for example, in order of increasing node IDs assigned at that time, then 0 is assigned to the DV 1502a and 1 is assigned to the DV 1502b. At this time, the node ID and the device number (1109) of each DV are as shown in the column of “BEFORE RESTART” in FIG. 24.
When the PC 1301 is restarted here, reassignment of device numbers (1109) for all DVs takes place. If, at this time, the node ID of the DV 1502a changes to 2 and the node ID of the DV 1502b changes to 1 shown in FIG. 24, then the device number 1 is assigned to the DV 1502a and 0 to the DV 1502b. 
Next, the method of controlling the operation of the DV 1502a and DV 1502b from the PC 1301 will be described.
Assuming that the device number of the DV 1502a is 0, for example, if it is desired to instruct the DV 1502a to perform a particular operation, 0 as the device number (1109) corresponding to the DV 1502a and a command 1108 are input to the IEEE 1394 interface 1104. The IEEE 1394 interface 1104 transmits the command 1108 as a command 1108a via the IEEE 1394 bus 1103 to the DV 1502a corresponding to the received device number (1109). The IEEE 1394 interface 1504a receives the command 1108a thus transmitted to the DV 1502a via the IEEE 1394 bus 1103, and transfers it to a control circuit 1107a. The control circuit 1107a interprets the contents of the command 1108a and instructs the recording and playback circuit 1503a to perform the specified operation.
Next, the method of transmitting data from the PC 1301 to the DV 1502a will be described.
Assuming that the device number of the DV 1502a is 0, for example, if it is desired to transmit data 1505 to the DV 1502a, 0 as the device number (1109) corresponding to the DV 1502a and the data 1505a are input to the IEEE 1394 interface 1104.
Generally, the IEEE 1394 bus 1103 has a plurality of channels so that different data communications can proceed over the plurality of channels concurrently. For data communication, therefore, the channel must be specified.
Assume, for example, that the DV 1502a is using channel 63. At this time, to transmit the data 1505 to the DV 1502a designated by the device number (1109) of 0, the IEEE 1394 interface 1104 transmits the data 1505 over channel 63 on the IEEE 1394 bus 1103.
The IEEE 1394 interface 1504a receives the data 1505 thus transmitted to the DV 1502a via the IEEE 1394 bus 1103, and transfers it to the recording and playback circuit 1503a. The recording and playback circuit 1503a plays back and/or records the input data 1505. When playing back the data, the reproduced video image 1507a is output to the monitor 1506a. 
If, at this time, the DV 1502b is using channel 63, the DV 1502b also can receive the data 1505 at the same time.
In the above prior art configuration, however, when the user desires to control the operation of a DV from the PC, the user is required to specify the DV whose operation is to be controlled by using the device number assigned to the DV.
The PC assigns the device number to each DV during power on, but when a plurality of DVs are connected to the IEEE 1394 bus, the device number assigned to a DV may not be the same as the device number previously assigned to the DV. The prior art, therefore, has had the problem that the user cannot distinguish the DV whose operation is to be controlled, since the user does not know which device number is currently assigned to which DV.